Single-walled carbon nanotubes (SWNTs) are of commercial interest in applications ranging from ultra-small electronic and sensing devices to multifunctional materials (1). Examples include field effect transistors (2), field emission displays (7), and chemical sensors (3,6). Integration of the nanotube material depends on the ability to control the placement, orientation, and shape of the nanotube components within the context of the device on the micrometer- to nanometer-length scale. Positional control over large areas is important. Depending on the intended application, one wants to pattern SWNTs as individual tubes (3,4), small bundles (5), or thin films (6, 8, 9). SWNTs are but one example of nanotechnology building blocks, and other examples include nanotubes generally and nanowires.
Previous work has shown that individual carbon nanotubes can be positioned (10), bent (11), and even welded (12) with nanometer accuracy by using scanning probe instruments. This level of manipulation can be limited to serial and therefore slow processes than span relatively short distances (100 microns). Other assembly methods such as Langmuir-Blodgett techniques (13), external field assisted routes (14-19), electrospinning (20), transfer printing (21), and DNA templates (22, 23) also have been used for nanotube assembly. These parallel methods address the speed limitation posed by conventional scanning probe techniques, but thus far are quite limited with respect to registration control and have demonstrated only coarse placement capabilities.
One approach is to use patterned chemical templates to assemble SWNTs from solutions. For example, SWNTs can be positioned along straight line features comprised of amine-terminated self-assembled monolayers (SAMs) (9, 24-27). See also US patent publication 2004/0166233 (“Depositing Nanowires on a Substrate”) to Hong.
Additional background patent literature includes US Patent publications 2004/0245209 to Jung et al (published Dec. 9, 2004); 2005/0269285 to Jung et al. (published Dec. 8, 2005); and 2004/0101469 to Demers (published May 27, 2004).
A need exists, however, to better simultaneously control the position, shape, and/or linkage of nanotubes, nanowires, and in particular carbon nanotubes including SWNTs on the sub-micron scale to better provide sophisticated architectures including for example rings, electronic interconnects, and structured thin films.
A need exists to better adapt nanolithography to carbon nanotube including SWNT placement technology (28,29).
A listing of references is provided later herein for literature citations.